Multi-layer thermal insulation element for batteries

ABSTRACT

A multi-layer heat insulation element for thermal insulation of a battery is proposed, with a first cover layer, with a second cover layer and with a compressible and/or pliable intermediate ply arranged between the cover layers, which has at least one heat-resistant fibre layer, wherein the fibre layer is formed from a needled nonwoven and/or wherein the cover layers are flexurally weak and the heat insulation element as a whole is compressible and flexibly pliable.

The present invention concerns a multi-layer heat insulation element forthermal insulation of a battery according to the preamble of claim 1, abattery with a multi-layer heat insulation element according to thepreamble of claim 35, and a use of a multi-layer heat insulation elementaccording to the preamble of claim 49.

In the present invention, the term “heat insulation element” ispreferably to be understood as a flat component consisting of a layeredstructure, in particular a layer package, which is designed and/or usedfor the thermal insulation of a battery. In particular, the heatinsulation element is configured to reduce and/or delay the release ofheat to the environment, in particular a vehicle interior, and/or tocontain and/or reduce and/or delay the spread of heat in the battery inthe event of uncontrolled and/or excessive heat development in thebattery.

In the present invention, the term “battery” is to be understood asmeaning, in particular, a rechargeable storage element and/or secondaryelement for providing electrical energy by converting chemical energy.The battery is preferably composed of several interconnected accumulatorcells and/or cell blocks, i.e. battery cells.

In particular, the battery is configured as a traction battery and/orfor the drive of electric vehicles and/or as a lithium-ion battery.Here, reliable and/or effective thermal insulation is important in orderto protect the vehicle occupants in the event of the batteryoverheating, for example as a result of a traffic accident, at leastuntil the arrival of rescue services.

Due to their chemical composition, lithium-ion batteries in particularexhibit comparatively high instability. If a local short-circuit of theinternal electrodes in a battery cell occurs, for example due tocontamination of the separator separating the electrodes by trappedforeign particles and/or mechanical action or damage, the strongshort-circuit current heats the battery cell up to 800° C. in a shorttime, sometimes up to 1300° C. This process is known as thermal runaway.The thermal runaway of one battery cell can easily and/or quickly spreadto other, adjacent battery cells, especially since the separator losesstability at relatively low temperatures, for example above 120° C., andshort circuits can therefore quickly occur in adjacent battery cells.This leads to an unstoppable chain reaction, wherein the energy storedin the battery is released in a short time, usually explosively and withthe release of fragments.

Against this background, it is desirable to keep a battery cell locatedadjacent to a battery cell running away or overheating as long aspossible below a certain limit temperature, preferably 120° C., inparticular 80° C. Above 80° C. the aging process of the battery cell isconsiderably accelerated and above 120° C. the separator in the batterycell often begins to melt, accompanied by irreversible damage and/orshort circuits.

Likewise, there is a high demand for efficient and/or long-lasting heatprotection of adjacent areas and/or rooms, especially vehicle interiors,against uncontrolled heat development in the battery. In particular,occupants and/or objects should be protected from heat until rescueand/or recovery measures have been fully completed.

DE 101 34 145 A1 concerns a fire-retardant battery housing. The batteryhousing contains a thermally active material, for example aluminiumsilicate or gibbsite, which transforms above a certain temperature,whereby further supplied thermal energy is consumed for the progressivetransformation and thus a rise in temperature is at least slowed down.In this case, effective containment of thermal cycling is not or at bestonly very difficult to achieve, since it is not possible to arrange theprotective material between battery cells, the conversion can lead tomechanical stress or destruction of the battery cells, and there is arisk that the thermally active material will burst and thus lose itsthermal insulation function prematurely.

AT 518 161 A4 concerns a battery with a plurality of battery cells,wherein at least two adjacent battery cells are thermally insulated fromeach other by a protective material. Above a predetermined temperature,the protective material expands and the battery cells insulated from oneanother are pushed away from one another by the increase in volume ofthe protective material which expands under the effect of temperature,the battery cells thus being thermally further separated and/orinsulated from one another. The disadvantage is that the increase involume of the protective material—in particular in addition to theincrease in pressure due to the heat development—results in an inflationpressure within the battery, which correspondingly increases the risk ofthe battery bursting and/or of damage to and destruction of batterycells.

From U.S. Pat. No. 8,541,126 B2 a heat insulation element for thethermal insulation of a battery is known. The heat insulation element isarranged between two adjacent battery cells. The heat insulation elementhas a layered structure with an interlayer arranged between two coverlayers. The interlayer has a higher thermal conductivity than the coverlayers. The cover layers can be designed as a fibre layer of ceramic orrefractory fibres. A disadvantage is that the heat insulation element isbrittle due to the formation of the fibres and can burst and/or fragmenteven at low pressure loads. This is not only associated with asignificant impairment or even loss of the thermal insulation function,but also leads to damage to adjacent and/or neighbouring battery cellsand ultimately increases the risk of explosion.

EP 3 142 166 A1 concerns a heat insulation element with a rigid micaplate and a compressible, short-fibre and/or refractory fibre layer,which are alternately arranged and/or stacked on top of each other. Thedisadvantage is that a flexible adaptation and/or shaping, especiallyfor installation in a battery, is not possible. Also, the heatinsulation element with its brittle mica plates and its short-fibredfibre mat can easily burst and/or fragment as a result of anuncontrolled heat development and the associated pressure increase,leading to damage to the surroundings and/or prematurely losing itsthermal insulation function. Finally, the high mass per unit area isdisadvantageous especially for vehicles.

It is an object of the present invention to provide a multi-layer heatinsulation element for the thermal insulation of a battery, a batterywith such a heat insulation element and a use of the heat insulationelement, wherein efficient heat insulation and/or a robust and/orresistant construction and/or flexible and/or easy assembly and/orintegration into the battery is enabled and/or supported.

The above object is solved by a multi-layer heat insulation elementaccording to claim 1, by a battery according to claim 35 or by a useaccording to claim 49. Advantageous further developments are the subjectof the subclaims.

A first aspect of the present invention is that the fibre layer isformed of long fibres of more than 30 mm in length and/or of a needledor bonded nonwoven. The long fibres and/or the needling and/or bondingof the fibre layer significantly increase the mechanical resistancecompared to another fibre layer. Thus, the fibre layer according to theinvention is on the one hand stretchable and pressure-elastic, whichenables the absorption of high pressure forces. At the same time, thefibre layer has a high thermal insulation capacity, as the intertwinedfibres efficiently reduce the passage of thermal energy through thefibre layer. This is particularly advantageous in the event ofuncontrolled heat generation within the battery, for example when athermal runaway of a battery cell occurs, as this significantly delaysthe complete destruction or explosion of the battery. Finally, needlednonwovens have a low mass per unit area, which facilitates handling.

Preferably, the fibre layer is made of needled and/or bonded glassfibres or silicate fibres or a mixture thereof.

Particularly preferably, the fibres of the fibre layer have a length ofat least 40 mm, preferably at least 50 mm, in particular essentially 50to 60 mm. This allows a particularly high pressure and tear resistanceof the fibre layer.

In particular, the fibres have an average diameter of at least 4 μm,preferably at least 5 μm, in particular 6 to 15 μm.

The fibre layer is particularly preferred to be binder-free and/or freeof melt beads.

Preferably, the fibre layer and intermediate ply, respectively, has amass per unit area of less than 1000 g/m², preferably less than 800g/m², in particular less than 600 g/m², and/or more than 150 g/m²,preferably more than 200 g/m², in particular more than 300 or 400 g/m².This enables easy handling.

According to a second aspect of the present invention which can also berealised independently, the cover layers are designed to be flexurallyweak and/or flexurally soft in order to make the heat insulation elementboth compressible and flexible and/or elastically pliable. This enablesa flexible adaptation to different installation situations and/or abetter adaptation in case of high loads, e.g. bursting of a batterycell, so that the heat insulation element is more resistant todestruction and/or loss of its heat insulation function. Finally, therelease of fragments is significantly reduced.

Preferably, at least one cover layer is designed to be liquid-tight,preferably waterproof. In addition, one of the cover layers, preferablyboth cover layers, is/are designed to be water-repellent and/orgas-tight In this way, the intermediate ply and/or fibre layer isefficiently protected, thus ensuring efficient thermal insulation evenin humid and/or gaseous environments.

Preferably, at least one cover layer is designed as a heat-resistantmetal layer, preferably aluminium layer.

Alternatively, at least one cover layer may be formed as aheat-resistant plastic layer, preferably polyimide layer, or as aheat-resistant woven fabric layer, preferably glass fabric layer.

A cover layer designed as a metal, plastic or woven fabric layer ispreferably less than 100 μm, particularly preferably less than 80 μm, inparticular between 20 and 50 μm, thick.

According to a preferred design, the heat insulation element has a layerof a woven fabric. The woven fabric can form at least one cover layerand/or an additional layer. Preferably, the woven fabric is arranged onthe outside of the heat insulation element. The woven fabric maycomprise or consist of metal fibres, in particular stainless steelfibres and/or aluminium fibres, glass fibres, carbon fibres, silicatefibres and/or a mixture thereof. In particular, the mechanical stabilityof the heat insulation element can be significantly increased and/orimproved by using a woven fabric as a cover layer. This is particularlyadvantageous as mechanical protection in the event of a battery cellexplosion.

Preferably, at least one cover layer and/or the heat insulation elementis made air-permeable and/or gas-permeable, for example if the coverlayer comprises the woven fabric or is formed by it. This may reduce therisk of explosion of a battery enclosed and/or surrounded by one or moreheat insulation elements, as in this way explosive gases may bedischarged through the cover layer.

Particularly preferably, at least one cover layer or both cover layersis/are designed as heat-resistant mica layer, preferably mica paperlayer or mica board. In particular, a cover layer formed as a mica layeris less than 3 mm, preferably less than 2 mm, in particular less than 1mm, especially preferably between 0.05 and 0.15 mm, thick. This allows ahigh heat resistance and at the same time flexibility and/or pliability.

Particularly preferably, the first cover layer is designed as ahigh-temperature resistant mica layer, preferably mica paper layer,whereas the second cover layer is designed as an aluminium layer,preferably aluminium foil. Alternatively, the second cover layer canalso be designed as a plastic layer, preferably polyimide layer. Theabove-mentioned material pairing allows the thermal insulation to beoptimised. This has been confirmed by tests.

Particularly preferably, the intermediate ply comprises two fibrelayers, in particular of needled nonwoven, the fibre layers beingseparated from each other by a heat-resistant and/or flexurally weakinterlayer. The multi-layer structure thus formed (two or more heatinsulation and/or fibre layers separated by an interlayer) allows theheat insulation properties of the intermediate ply to be furtherimproved, since the interlayer within the intermediate ply forms athermal barrier between the fibre layers and thus further reduces and/orlimits the spread of heat through the intermediate ply and/or the heatinsulation element This has also been confirmed in tests.

Particularly preferably, the interlayer is designed as a hightemperature resistant plastic layer, preferably polyimide film, oraluminium layer, in particular aluminium foil.

The interlayer is preferably less than 100 μm, especially preferablyless than 80 μm, in particular between 20 and 50 μm, thick.

Preferably, at least one cover layer and/or the interlayer has adielectric strength of more than 1 kV/mm, preferably more than 1.5kV/mm, in particular more than 2 kV/mm. This avoids and/or delays theformation of electric arcs or sparks.

In particular, the heat insulation element—preferably when installed—isless than 7 mm, preferably less than 6 mm, in particular between 2 and 3mm, thick. This allows a flexible and easy installation in the battery,even in narrow installation gaps.

In particular, the heat insulation element has an adhesive layer on atleast one flat side at least in sections or is self-adhesive at least insections on one flat side. This allows the heat insulation element to beeasily arranged and/or attached to or in the battery and/or further heatinsulation elements.

Preferably, the cover layers and the intermediate ply are glued togetheror otherwise joined to form a bond. In this way, a mechanically stablelayered composite is realised.

In particular, the heat insulation element has a dielectric strength ofmore than 20 kV/mm, preferably more than 30 kV/mm, in particular of 40to 70 kV/mm.

Preferably, the heat insulation element has a mass per unit area of lessthan 1500 g/m², preferably less than 1300 g/m², in particular less than1000 g/m², and/or more than 150 g/m², preferably more than 200 g/m², inparticular more than 300 or 400 g/m².

The thermal conductivity of the heat insulation element at 25° C. roomtemperature is less than 0.1 W/mK, preferably less than 0.08 W/mK, inparticular less than 0.04 W/mK.

A battery, preferably a lithium-ion battery, according to the proposal,in particular in the form of a traction battery for an electric vehicle,comprises a housing and at least one multi-layer heat insulation elementaccording to the proposal, which is arranged in and/or on the housingfor thermal insulation. This results in corresponding advantages.

Preferably, the heat insulation element closes and/or insulates thebattery or battery cells or the housing on the outside or inside on thetop surface at least partially, preferably completely or over the entiresurface. This allows effective heat insulation of the battery towardsthe top and/or towards an area located above and/or adjacent to thebattery, in particular a vehicle interior of a vehicle. In this way,persons, occupants and/or objects in the area and/or room are protectedeffectively and/or for a sufficiently long time—i.e. until rescue and/orrecovery measures have been completed—from uncontrolled heat developmentin the battery.

Alternatively or additionally, the heat insulation element can be placedbetween two adjacent battery cells in the housing and thermally insulatethem from each other. In this way, flashing over of a thermal runawayfrom one battery cell to the next and/or adjacent battery cell iseffectively delayed and/or contained, thus preventing or at leastsignificantly delaying the explosive release of heat and/or fragmentsfrom the battery.

In particular, the heat insulation element is attached and/or fixed toor in a housing lid and/or housing top part of the housing, preferablyglued on.

The heat insulation element can be attached, especially over its entiresurface, to an inner side of the housing or housing lid facing thehousing interior and preferably on top in the installed state. In thisway, effective top-side heat insulation is made possible.

Alternatively or additionally, the heat insulation element and/oranother heat insulation element may be attached or aligned transverselyand/or perpendicularly to the inside, in particular in such a way thatthe heat insulation element can be easily inserted between two adjacentbattery cells.

Alternatively or additionally, the heat insulation element and/oranother heat insulation element can be arranged on the inside on a floorand/or the underside of the housing interior. In this way it is possibleto protect the battery against heat acting on the battery from theunderside, for example in the event of a fuel fire on the road.

Alternatively or in addition, the heat insulation element and/or anotherheat insulation element can be arranged on the inside of a side wall ofthe housing and/or a side wall of the interior.

Preferably, at least two heat insulation elements are arranged in thebattery, wherein at least one first heat insulation element insulatesthe housing and/or the housing interior at the top and at least onesecond heat insulation element is arranged between adjacent batterycells. In this way, corresponding advantages, which can in principlealso be realised independently of one another, can be realisedsimultaneously, i.e. top-side heat insulation of the battery on the onehand and delay and/or reduction of heat propagation between adjacentbattery cells, packs or modules on the other.

In particular, the second heat insulation element is attachedtransversely and/or vertically to the first heat insulation element,preferably glued, sewn or otherwise firmly connected.

In the case of a battery according to the proposal, it is particularlyadvantageous if the heat insulation element has at least one cover layerand/or additional layer of a woven fabric, preferably metal mesh, inparticular wire mesh of stainless steel. As mentioned above, this mayallow explosive gases to escape through the cover layer, thus reducingthe risk of the battery exploding.

In addition, a cover layer or additional layer of woven fabricpreferably offers high mechanical stability, so that passengers in thevehicle interior can be effectively protected from fragments in theevent of a battery explosion.

It is also possible that a filter function for explosive and/or toxicand/or harmful gases is provided by the woven fabric, so that passengersin the vehicle interior are protected from such gases. Preferably, thewoven fabric is designed in such a way that at least some of the gasesare separated at the woven fabric. This will reduce the risks to humansresulting from such gases and/or exhaust gases.

In general, it should be noted that the proposed aspects according tothe present invention improve and/or simplify the thermal insulation andfire protection of the passenger compartment of batteries, especiallyfor electric vehicles. In particular, the proposed heat insulationelement makes possible very effective heat insulation between thebattery on the one hand and a vehicle interior, preferably located aboveand/or adjacent to the battery, on the other. Alternatively oradditionally, a transfer of heat and/or the thermal runaway of a batterycell to adjacent battery cells is delayed and/or contained, thuspreventing or at least significantly delaying the destruction and/orexplosion of the battery. In this way, sufficient time is provided forrescue and/or recovery, within which the occupants are adequatelyprotected from the uncontrolled heat development in the battery.

The above-mentioned aspects and features of the present invention aswell as the aspects and features of the present invention resulting fromthe claims and the following description can basically be realisedindependently of each other, but also in any combination and/orsequence. Additional advantages, features, properties and aspects of thepresent invention result from the claims and the following descriptionof preferred embodiments based on the drawing. It shows:

FIG. 1A a schematic section of a proposed multi-layer heat insulationelement for thermal insulation;

FIG. 1B a schematic section of a multi-layer heat insulation elementaccording to another embodiment;

FIG. 1C a schematic section of a proposed heat insulation elementaccording to another further embodiment;

FIG. 1D a schematic representation of a woven fabric;

FIG. 2 a schematic section of a battery with heat insulation elementsarranged therein, which is arranged and/or installed in a schematicallyindicated vehicle;

FIG. 3 a schematic section of a battery with an ordered heat insulationelement according to a further embodiment;

FIG. 4 a first experimental setup for carrying out temperaturemeasurements on proposed heat insulation elements;

FIG. 5 a second experimental setup for carrying out temperaturemeasurements on proposed heat insulation elements;

FIG. 6 a first temperature diagram, measured on a proposed heatinsulation element with a first layer structure; and

FIG. 7 a second temperature diagram, measured on a proposed heatinsulation element with a second layer structure.

FIG. 1A shows in a schematic, not to scale sectional view a multi-layerheat insulation element 1 according to the proposal. FIGS. 1B and 1Cshow in a likewise schematic, not to scale sectional view furtherembodiments of the multi-layer heat insulation element 1 according tothe proposal. The embodiments shown are similar to each other and canalso be combined with each other as desired. In particular, thedifferent FIGS. 1A, 1B and 1C serve only to highlight differentpreferred aspects.

The heat insulation element 1 is in particular designed as a flat layerpackage.

The heat insulation element 1 is in particular compressible and at thesame time pliable.

The term “pliable” is preferably understood to mean a sufficiently lowbending stiffness of the heat insulation element 1, wherein the bendingstiffness is a measure of the resistance of an acting force to bendingdeformation for a component and/or the heat insulation element 1. Thebending stiffness is preferably determined according to ISO 5628 2493.For this purpose, a plate-shaped heat insulation element 1 with acertain dimension, for example with a thickness of 6 mm and a size of 60mm×40 mm, is clamped in a rotatable clamping device. The free end of theheat insulation element 1 touches a sensor of a load cell, via which acorresponding contact force is recorded when the clamping device isrotated. In particular, the sensor contacts the free end of the heatinsulation element 1 at a distance of 50 mm from the clamping point. Thebending stiffness is determined in particular by the force measured atthe sensor when the heat insulation element is bent by 15°. Preferably,the heat insulation element 1 has a bending stiffness determined in thisway of less than 10 N, preferably less than 5 N, in particular less than1 N.

The term “compressible” is preferably understood to mean a sufficientlylow compression hardness of the heat insulation element 1, thecompression hardness representing a pressure required to compress a testspecimen and/or the heat insulation element 1 by 40% of its originalthickness. The compression hardness is preferably determined inaccordance with DIN EN ISO 3386, using a plate-shaped heat insulationelement 1 with a thickness of 5 mm and a size of 300 mm×200 mm as thetest specimen and an aluminium plate with a thickness of 20 mm and asize of 190×80 mm as the indenter. Preferably, the heat insulationelement 1 has a compression hardness determined in this way of less than40 kPa, preferably less than 30 kPa, in particular less than 20 kPa.

The heat insulation element 1 is especially configured for the thermalinsulation of a battery 8 shown in FIG. 2. A preferred structure ofbattery 8 and a preferred arrangement of heat insulation elements 1A, 1Bin battery 8 will be discussed later.

The heat insulation element 1 has a first cover layer 2 and a secondcover layer 3. The cover layers 2, 3 each form in particular one (outer)flat side of the heat insulation element 1.

Preferably, a compressible and/or pliable intermediate ply 4 is arrangedbetween the cover layers 2, 3. The intermediate ply 4 has at least onefibre layer 5—in the example shown two or more fibre layers 5.

One or each fibre layer 5 is preferably formed from a needled and/orbonded nonwoven. For the purposes of the present invention, the term“needled nonwoven” is preferably to be understood as a textile fabric,the fibres of which are randomly intertwined and thereby bonded by dryneedling and/or needling without binder and/or melting beads.

The fibre layers 5 are in particular made of glass fibres or silicatefibres or a mixture thereof. For example, glass fibres, in particular ofE-, ECR- or R-glass or mixtures thereof, and/or other heat-resistantfibres may be used.

The fibres preferably have an average diameter of at least 4 μm, inparticular at least 6 μm, and most preferably essentially 8 to 16 μm.

The length of the fibres is preferably more than 30 mm, preferably morethan 40 mm, in particular essentially 50 to 60 mm. In principle,however, the length of the fibres can also be greater, for example up toabout 120 mm.

Preferably, the fibre layers 5 are free of binding agents and/or meltingbeads.

Preferably, the mass per unit area of the fibre layers 5 and/or theintermediate ply 4 is less than 1000 g/m², preferably less than 800g/m², in particular less than 600 g/m², and/or more than 150 g/m²,preferably more than 200 g/m², in particular more than 300 or 400 g/m².

Preferably, the mass per unit area of the heat insulation element 1 isless than 1500 g/m², preferably less than 1300 g/m², in particular lessthan 1000 g/m², and/or more than 150 g/m², preferably more than 200g/m2² in particular more than 300 or 400 g/m².

Preferably, the fibre layers 5 of the intermediate ply 4 are separatedfrom each other by an interlayer 6. The interlayer 6 is in particularformed by a heat-resistant metal layer, preferably aluminium layer.However, the interlayer 6 may also be formed by a heat-resistant plasticlayer, preferably polyimide layer.

The heat insulation element 1 can also have several interlayers 6 andcorrespondingly several fibre layers 5, in particular wherein two fibrelayers 5 are separated from each other by an interlayer 6.

The cover layers 2, 3 are preferably designed to be flexurally weak,i.e. easily pliable and/or flexible. A “flexurally weak” cover layer 2,3 in the sense of the present invention is preferably paper-like,fabric-like or foil-like and/or has a thickness of less than 2 mm, inparticular less than 1 mm. Especially preferably, the thickness of thecover layer 2, 3 is more than 0.05 mm and/or less than 0.15 mm. Thismakes the entire heat insulation element 1 compressible and flexible,the compressibility being at least essentially due to the compressibledesign of the intermediate ply 4.

The cover layers 2 and 3, intermediate ply 4, fibre layers 5 and/or theheat insulation element 1 is or are preferably heat-resistant, inparticular up to at least 200° C., particularly preferably above 250°C., 500° C. or 1000° C.

Preferably, at least one of the cover layers 2, 3 is configured as aheat-resistant metal layer, preferably aluminium foil, or as aheat-resistant plastic layer, preferably polyimide foil, or as aheat-resistant woven fabric layer, preferably glass fabric foil, or as amica layer, preferably mica paper layer.

Particularly preferably, one and/or the first cover layer 2 isconfigured as a heat-resistant mica layer, preferably mica paper layer,and the other and/or the second cover layer 3 is configured as a metallayer, preferably aluminium foil, or plastic layer, preferably polyimidefoil. However, both cover layers 2, 3 may also be identically designed,in particular as a mica layer, preferably mica paper layer. This makespossible a particularly high heat resistance.

An embodiment of the heat insulation element 1, in which the coverlayers 2, 3 are identically designed, for example each as a mica layer,is shown in particular in FIG. 1B.

According to a further embodiment, the heat insulation element 1 canhave a woven fabric 21. The woven fabric 21 preferably forms an at leastsubstantially planar and/or flat layer and/or woven fabric layer.

The term “woven fabric” refers in particular to a preferably flatproduct which is formed by a plurality of threads or wires crossing eachother in particular at least substantially at right angles. The threadsand/or wires are guided over and under transverse threads and/or wires,in particular in a certain rhythm and/or a repetitive sequence.

Preferably, the woven fabric 21 forms one or both cover layers 2, 3.However, it is also possible that the woven fabric 21 forms anadditional layer 22, which is preferably provided in addition to thecover layers 2, 3. The additional layer is shown in FIG. 1C.

The woven fabric 21 is preferably a metal mesh, in particular a wiremesh made of stainless steel and/or aluminium. However, the woven fabric21 can also be a glass fibre fabric, a carbon fibre fabric or a silicatefabric. It is also possible that the woven fabric 21 is a blended fabricand/or has or consists of a mixture of metal fibres, in particularstainless steel fibres and/or aluminium fibres, glass fibres, carbonfibres and/or silicate fibres.

The additional layer 22 is preferably arranged on the outside of theheat insulation element 1. Alternatively, the additional layer 22 can beprovided inside the heat insulation element 1, for example between thecover layer 2, 3 and the fibre layer 5 and/or between the fibre layer 5and the interlayer 6.

The cover layer 2, 3 of a woven fabric 21 is laminated and/or gluedpreferably to the fibre layer 5 or otherwise firmly connected to thefibre layer 5. Particularly preferably, an air-permeable and/orgas-permeable adhesive is used for connecting the woven fabric 21forming a cover layer 2, 3 to the fibre layer 5, preferably wherein theadhesive allows gases to escape and/or pass through but forms a barrierto sparks or flames. This is particularly advantageous when using theheat insulation element 1 in a battery 8, which is described in moredetail below.

Furthermore, embodiments are possible in which the heat insulationelement 1 has both the additional layer 22 and the adhesive layer 7,preferably wherein in this case the adhesive layer 7 is arranged at thefirst cover layer 2 and the additional layer 22 is arranged at thesecond cover layer 3 or vice versa.

The woven fabric 21 preferably has a high heat resistance, preferably upto a temperature of about 1150° C.

The woven fabric 21, in particular metal mesh, preferably has a meshsize of at least 0.1 mm and/or at most 0.4 mm. Particularly preferredmesh sizes are, for example, about 0.114 mm, about 0.22 mm and about0.315 mm.

The woven fabric 21, in particular metal mesh, preferably has an openscreening area of at least 30% and/or at most 60%. Particularlypreferred open screening areas are, for example, about 37.0%, about42.4% and about 51%.

Preferably, at least one cover layer 2, 3 and/or the additional layer22, in particular the woven fabric, is gas permeable.

Preferably, at least one cover layer and/or the additional layer 22, inparticular the woven fabric 21, is designed in such a way thatexplosive, toxic and/or harmful gases are filtered and/or absorbed, forexample mechanically and/or chemically, when passing through the heatinsulation element 1, the cover layer 2,3 and/or the additional layer22.

Preferably, at least one cover layer 2, 3 and/or the additional layer22, in particular the metal mesh and/or the heat insulation element 1 asa whole, has such mechanical stability that no fragments can penetratethe heat insulation element 1 in the event of an explosion of battery 8.

The heat insulation element 1 preferably has a thickness of less than 15mm, preferably less than 10 mm, in particular between 6 and 8 mm, inparticular in the uncompressed state or delivery state.

Particularly preferably, the heat insulation element 1 and/or at leastone cover layer 2, 3 and/or the interlayer 6 has a dielectric strengthof more than 20 kV/mm, preferably more than 30 kV/mm, in particular of40 to 70 kV/mm.

The cover layers 2, 3 and the intermediate ply 4 are connected to eachother, in particular by gluing. In particular, a heat-resistant adhesiveis used for this purpose. However, other connection techniques, such assewing or welding, are also possible.

Preferably and/or optionally, at least one cover layer 2, 3—in theillustration example the first cover layer 2—has an adhesive layer 7, inorder to attach and/or fix the heat insulation element 1 to a part ofthe battery 8 and/or to another heat insulation element 1 as required.

The adhesive layer 7 consists in particular of an acrylate adhesive.

The mass per unit area of the adhesive layer 7 is preferably less than150 g/m², preferably less than 120 g/m², in particular between 50 and100 g/m². Alternatively or additionally, adhesive layer 7 may also be inthe designed as a double-sided adhesive tape.

However, adhesive layer 7 is not mandatory, but merely optional, as canbe seen in particular from FIGS. 1B and 1C.

In the following, an arrangement according to the proposal and/or a useof heat insulation elements 1A and 1B according to the proposal andoptionally further heat insulation elements 1C and 1D according to theproposal in battery 8 is explained in more detail on the basis of FIG.2. The heat insulation elements 1A to 1D can be designed identically ordifferently in accordance with the embodiments explained above.

In the following, the heat insulation elements 1A to 1C are referred toas first heat insulation element 1A, second heat insulation element 1B,third heat insulation element 1C and fourth heat insulation element 1Dfor differentiation. However, this only serves to differentiate thedifferent heat insulation elements and does not imply that, for example,if the third heat insulation element 1D is provided, a second heatinsulation element 1B must also be present.

In particular, the battery 8 for power supply is arranged and/orinstalled in a schematically depicted vehicle 14, especially an electricvehicle. In particular, when installed, battery 8 is located below avehicle interior 15, for example a passenger or other interior area ofthe vehicle 14.

The battery 8 preferably has a housing 9 with a lower housing part 10and an upper housing part and/or housing lid 11. The housing 9preferably consists of a non-conductive material, for example plastic,or of metal.

The battery 8 is preferably designed as a rechargeable lithium-ionaccumulator. Alternatively, it can also be constructed or designed fromor with lithium iron phosphate, lithium cobalt oxide, lithium metaloxide, lithium ion polymer, nickel zinc, nickel metal, nickel cadmium,nickel hydrogen, nickel silver, nickel metal hybrid and similar systemsand/or materials.

In particular, the battery 8 has at least one group of battery cells 12which are electrically interconnected and housed in housing 9,preferably in the lower housing part 10.

A first heat insulation element 1A is attached and/or fixed above thebattery cells 12 and/or on the housing lid 11 of the housing 9,preferably by means of adhesive, especially by means of the adhesivelayer 7.

Particularly preferably, the first heat insulation element 1A is mountedover its entire surface on an inner side 13 of the housing lid 11, theinner side 13 facing the housing interior. The first heat insulationelement 1A thus closes and/or insulates the lower housing part 10 and/orthe battery 8 and/or its cells 12 on the top side.

In this way, a particularly efficient top-side heat insulation and fireprotection against the vehicle interior 15 is achieved, in order toprotect persons or objects inside efficiently and/or long enough fromuncontrolled heat development in the battery 8. A gas-tight constructionalso prevents and/or reduces gas explosion-like propagation in thedirection of the passenger compartment.

Particularly preferably, the second cover layer 3 of the first heatinsulation element 1A facing the interior of the housing and/or thebattery cells 12 is designed as a mica layer, preferably a mica paperlayer, the first cover layer 2 facing away from the battery cells 12and/or the interior of the housing being designed for fastening to thehousing lid 11 and in particular being provided with the adhesive layer7. This improves the heat resistance and at the same time facilitatesthe handling and/or fastening of the heat insulation element 1 to thehousing 9.

Alternatively or additionally, at least one (further and/or second) heatinsulation element 1B is arranged between adjacent battery cells 12, inthe illustration example between two groups of battery cells 12, wherebythe groups are thermally insulated and/or separated from each other.

Particularly preferably, the heat insulation element 1B is inserted,pressed in or in another way placed between the battery cells 12.

In particular, the heat insulation element 1A and/or 1B encloses and/orenvelops at least one battery cell 12 or a group of battery cells 12,preferably on all sides, and/or in particular in such a way that thebattery cell 12 and/or group of battery cells 12 is mounted and/orarranged in a damping manner in the housing 9 via the heat insulationelement 1A and/or 1B. In addition to effective, in particular all-round,heat insulation, this also enables the battery cells 12 to be mounted ina robust and/or resistant manner, since any shocks and/or vibrations aredamped and/or absorbed by the compressible heat insulation element 1Aand/or 1B.

In particular, the second heat insulation element 1B is attachedtransversely and/or perpendicularly to the inner side 13 of the housinglid 11 and/or aligned vertically, in particular in such a way that it isinsertable between the battery cells 12 when the housing lid 11 isplaced on the lower housing part 10.

The second heat insulation elements 1B are optionally attached and/orfastened transversely and/or vertically to the first heat insulationelement 1A, for example by gluing, sewing or in any other way.

The battery 8 can have a plurality of second heat insulation elements1B. Preferably, between several battery cells 12, in particular betweenall battery cells 12, second heat insulation elements 1B are arrangedand/or provided. In FIG. 3, a battery 8 with several heat insulationelements 1B is shown schematically.

As an alternative or in addition to the first heat insulation element 1Aand/or the second heat insulation element 1B, the battery 8 may have afurther and/or third heat insulation element 1C, as shown for example inFIG. 3. The third heat insulation element 1C is preferably arrangedopposite the first heat insulation element 1A and/or on an undersideand/or bottom of the housing interior 13, in particular on the innerside 13 of the housing 9. Preferably, the underside and/or bottom iscovered completely and/or over its entire surface by the third heatinsulation element 1C.

In particular in addition to the first heat insulation element 1A,second heat insulation element 1B and/or third heat insulation element1C, a further and/or fourth heat insulation element 1D may also beprovided. Preferably, the further and/or fourth heat insulation element1D is provided and/or arranged on one or more side walls of the insideand/or the housing 9. Preferably, the side wall(s) is/are completelycovered and/or thermally insulated by the fourth heat insulation element1D.

Preferably, in the battery 8 and/or housing 9, the woven fabric layerand/or woven fabric 21—if present—is arranged on the side of the heatinsulation element 1A, 1C, 1D facing the inner side 13.

Preferably, the heat insulation elements 1A, 1C, 1D are arranged on theinner side 13 and/or in the interior of the housing 9.

The heat insulation elements 1A-1D are preferably each arranged betweena battery cell 12 and/or the battery cells 12 and the housing 9.

The battery cells 12 are preferably at least substantially completelyand/or on all sides enclosed and/or surrounded by one or more heatinsulation elements 1A-1D.

The battery 8 and/or the housing 9 may have an outlet 23 for the escapeof gases. This is shown as an example in FIG. 3.

The outlet 23 is preferably located in the housing lid 11 and/or on atop side of the battery 8 and/or housing 9. Preferably, the outlet 23 isformed by an opening penetrating the housing lid 11 and/or the heatinsulation element 1A. The outlet 23 allows gases to escape from thehousing 9, thus reducing the risk of explosion.

The outlet 23 may have a filter 24 for gases and/or a valve 25, inparticular a one-way valve. By the valve, it can be ensured that gasescan escape from the battery 8 but that no gases can enter the battery 8.

FIGS. 4 and 5 schematically show test setups and/or test arrangementsfor carrying out temperature measurements on heat insulation elements 1according to the proposal.

In the tests carried out, the heat insulation function and/or heatinsulation capacity of the proposed heat insulation elements 1 wasinvestigated. For this purpose, heat was specifically introduced intothe housing 9 and/or a comparable structure via a heating element 16,preferably a heating foil, in order to simulate temperature conditionscomparable to those in the case of uncontrolled heat generation and/orthermal runaway. The resulting temperature diagrams and/or temperaturecurves are shown in FIG. 6 for a heat insulation element 1 with a firstlayer structure and in FIG. 7 for a heat insulation element 1 with asecond layer structure.

In the test set-up shown in FIG. 4, to simulate uncontrolled heatgeneration and/or thermal runaway, the heating element 16 was insertedbetween a battery cell 12′—located at a second position starting fromthe heat insulation element 1—and a battery cell 12″—located at a thirdposition starting from the heat insulation element 1—and continuouslyheated to a temperature above 120° C., preferably above 200° C.

At the same time, the resulting temperature curve and/or temperaturerise at the heat insulation element 1 on a cold side 17 facing away fromthe heating element 16 on the one hand and a hot side 18 facing theheating element 16 on the other hand was measured with a measuringdevice, in particular a thermocouple, wherein two measurements werecarried out for each layer structure.

The curves M1 and M2 in FIG. 6 show for each measurement the resultingtemperature curve on the cold side 17 of the heat insulation element 1with the first layer structure and the curves M1 and M2 in FIG. 7 showcorresponding temperature curves for a heat insulation element 1 with adifferent and/or second layer structure.

In general, the test setup shown in FIG. 4 is intended to investigateand/or verify the heat insulation function with regard to thecontainment and/or delay of the transfer of thermal energy to adjacentbattery cells 12 within the housing 9.

The second test setup as shown in FIG. 5 differs from the first testsetup in that the temperature curve is determined on a heat insulationelement 1 running on the upper side to the battery cells 12. This isintended to investigate and/or verify the heat insulation functionand/or heat insulation against a room adjacent to battery 8, inparticular the vehicle interior 15.

For this purpose, analogous to the first experimental setup, the heatingelement 16, in particular the heating foil, is arranged between adjacentbattery cells 12 and heated to at least 120° C., preferably at least200° C., to simulate uncontrolled heat generation and/or thermalrunaway. The temperature progression and/or temperature rise wasrecorded by means of a measuring means, in particular a thermocouple, onthe cold side 19 of the heat insulation element 1 remote from theheating element 16 on the one hand and on a hot side 20 of the heatinsulation element 1 facing the heating element 16 on the other hand.

The curve M3 in FIG. 6 shows the resulting temperature curve on the coldside 19 of the heat insulation element 1 with the first layer structureand the curve M3 in FIG. 7 shows the resulting temperature curve for thesecond layer structure.

In the temperature diagram shown in FIG. 6, a heat insulation element 1with the following first layer structure was used:

Name/Designation Preferred configuration Preferred thickness First coverlayer 2 Aluminium foil  50 μm Fibre layer 5 Reinforced needled   3 mmnonwoven glass fibre fabric Second cover layer 3 Mica paper layer 0.5 mmOverall structure approx. 5 mm (<2 mm when installed)

The X axis represents the time course in minutes. The axis starts with“0”, which marks the starting point for switching on the heating foil16.

The Y axis represents the temperature in ° C. The curves start at justover 20° C., which is essentially the ambient temperature.

As already mentioned, a temperature below 120° C., in particular below80° C., should be maintained on the cold side 17 and/or 19 for as longas possible to avoid damage and/or a short circuit and/or to preventtotal destruction and/or explosion of the battery 8, in particular toprotect the vehicle interior 15 from the release of heat, gases and/orfragments for a sufficiently long time.

The highest temperature for all measurements was measured on curve M3(i.e. on the cold side 19, FIG. 5) at 115.4° C. after approx. 30 min. Inthis case, the maximum temperature on the opposite hot side 20 was 837°C.

In curve M1 (first measurement on cold side 17, FIG. 4) a maximumtemperature of 92.75° C. was reached after approx. 20 min. In this case,the maximum temperature on the opposite hot side 18 was 730° C.

In curve M2 (second measurement on cold side 17, FIG. 4) the maximumtemperature of 89° C. was also reached after approx. 20 minutes. In thiscase, the maximum temperature on the opposite hot side 18 was 728° C.

The curves M1 and M2 deviate—as expected—only slightly from each other,as they are two measurements of the same test series (test setup FIG.4).

A comparison of curve M3 (test setup FIG. 5) on the one hand with curvesM1 and M2 (test setup FIG. 4) on the other hand initially shows that thehighest temperature (115.4° C.) was measured on cold side 19. However,this temperature is only reached after more than 30 minutes—and thussignificantly later than with the other curves M1 and M2. Until about 25min after the heat is introduced, curve M3 runs clearly below the othertwo curves M1 and M2 and only then rises. In this respect, in particularin the first 20 to 25 minutes, efficient heat insulation on the coldside 19 and thus a high level of heat insulation against a room and/orvehicle interior 15 adjoining on the top side is made possible.

In addition, the results show that the transfer of heat and/or thethermal runaway to adjacent battery cells 12 is efficiently delayedand/or contained, as the maximum limit temperature of 120° C. is notreached in all curves M1 to M3. This eliminates or at least minimizesthe risk of damage and/or short circuits.

Furthermore, the first layer structure can be realised comparativelyinexpensively.

Within the framework of the second temperature diagram shown in FIG. 7,a proposed heat insulation element 1 with the following second layerstructure was used:

Name/Designation Preferred configuration Preferred thickness First coverlayer 2 Aluminium foil  50 μm Fibre layer 5 Bonded nonwoven   5 mm glassfabric Interlayer 6 Polyimide film  25 μm Fibre layer 5 Reinforcednonwoven   5 mm glass fabric Second cover layer 3 Mica paper layer 0.2mm Overall structure approx. 10 mm (<3 mm when installed)

The X axis represents the time course in minutes. The axis starts with“0”, which initiates the starting point of switching on the heatingfoils 14 and/or 15 to initiate heat development in the correspondinggroups of battery cells 12A-E (see FIG. 5).

The Y axis represents the temperature in ° C. The curves start at justover 20° C., which is essentially the ambient temperature.

The highest temperature for all measurements was determined at 76.5° C.on curve M1 (i.e. on the cold side 17 in the first measurement, FIG. 4)after 10 minutes. In this case, the maximum temperature on the oppositehot side 18 was 1300° C.

For curve M2, a maximum temperature of 75° C. was reached—in the secondmeasurement according to FIG. 4—after 35 minutes on the cold side 17. Inthis case, the maximum temperature on the opposite hot side 20 was 1000°C.

For curve M3, a maximum temperature of 70° C. was reached on the coldside 19 after 55 minutes. In this case, the maximum temperature on theopposite hot side 20 was 730° C.

Consequently, the preferred maximum limit temperature of 80° C. was notreached in all cases, so that even accelerated aging of the adjacentbattery cell is avoided or at least reduced.

A comparison of curve M3 (test setup FIG. 5) on the one hand with curvesM1 and M2 (test setup FIG. 4) on the other shows that on the cold side19 (curve M3) not only is the lowest maximum temperature (70° C.)present, but this maximum temperature is also present much later, afterapprox. 55 min. Nevertheless, the lowest temperature (730° C.) was alsodetermined on the corresponding hot side 20.

Furthermore, it can be seen from FIG. 7 that a significant temperatureincrease in one of the curves M1 to M3 is only recorded after a time Tof about 11 to 12 minutes.

The course explained in FIG. 6 is also confirmed in that on cold side19, especially in the first minutes of heat input—in FIG. 7 until afterapprox. 45 minutes—the temperature is significantly lower than on coldside 17 (curves M1 and M2). In this respect, the heat insulation element1 with the second layer structure makes possible a particularlyeffective heat insulation against adjacent rooms and/or areas, inparticular the vehicle interior 15.

A comparison of the curves M1 to M3 of FIG. 7 (second layer structure)with the corresponding curves of FIG. 6 (first layer structure) alsoshows that a further improved heat insulation function can be achievedwith the second layer structure. In particular, a reduction of themaximum temperatures was achieved, wherein the difference in the curvesM3 (first layered construction: 115.4° C. compared to the second layeredconstruction: 70.0° C.) is particularly significant This proves theparticularly advantageous use of the second layer structure as top-sideheat insulation.

In general, due to the multi-layer structure of the intermediate ply 4,in particular with the polyimide layer arranged therein as interlayer 6,the second layer structure permits an optimum reduction of the heattransfer and thus a particularly efficient heat insulation function.

The polyimide layer protected by the nonwoven has retained its structureeven after thermal explosion, so that the electrical insulation ismaintained.

Overall, the tests show that the proposed heat insulation element 1 issuitable both for the containment of heat within battery 8 and fortop-side arrangement and/or insulation, i.e. especially for thermalprotection of adjacent vehicle interiors 15. The efficiency is optimalwith the second layered composite, wherein the first layered compositeallows a comparatively low-cost implementation with a likewise effectivethermal insulation function.

The present invention also concerns the use of the proposed heatinsulation element 1 on and/or in a battery 8, preferably a lithium-ionbattery, in particular a traction battery for an electric vehicle.

In particular, a heat insulation element 1 is placed on top of thehousing 9 to provide thermal insulation on the top side.

Alternatively or additionally, a heat insulation element 1 for thermalinsulation is arranged between two adjacent battery cells 12.

In particular, the heat insulation element 1 is attached and/or fixed,preferably with adhesive, to a housing lid 11 and/or the upper part ofthe housing 9.

Particularly preferably, the heat insulation element 1 is mounted,especially over its entire surface, on an inner side 13 of the housinglid 11 facing the housing interior.

Preferably, the heat insulation element 1 is mounted and/or alignedtransversely and/or perpendicularly to the inner side 13.

In particular, at least one first heat insulation element 1A and atleast one second heat insulation element 1B are used, the first heatinsulation element 1A closing and/or thermally insulating the housinginterior at the top and the second heat insulation element 1B beingarranged between adjacent battery cells 12A-E.

Preferably, the second heat insulation element 1B is attached to thefirst heat insulation element 1A, in particular transversely and/orvertically, preferably glued, needled or welded.

Individual aspects of the present invention can, as already mentioned,be combined as desired, but also realised independently of each other.

LIST OF REFERENCE NUMBERS

1 heat insulation element

1A (first) heat insulation element

1B (second) heat insulation element

1C (third) heat insulation element

1D (fourth) heat insulation element

2 first cover layer

3 second cover layer

4 intermediate ply

5 fibre layer

6 interlayer

7 adhesive layer

8 battery

9 housing

10 lower housing part

11 housing lid/upper housing part

12, 12′, 12″ battery cell

13 inner side

14 vehicle

15 vehicle interior

16 heating element

17 cold side vertical

18 hot side vertical

19 cold side horizontal (above the battery)

20 hot side horizontal (above the battery)

21 woven fabric

22 additional layer

23 outlet

24 filter

25 valve

M curve

T time

X axis

Y axis

1-49. (canceled)
 50. A battery, preferably lithium-ion battery, inparticular traction battery for an electric vehicle, with a housing, andwith at least one multi-layer heat insulation element arranged in theinterior of the housing for thermal insulation and fire protection,wherein the heat insulation element is provided with a first coverlayer, with a second cover layer, and with a compressible and pliableintermediate ply arranged between the cover layers, which comprises atleast one heat-resistant fibre layer, wherein the fibre layer is formedfrom a needled nonwoven.
 51. The battery according to claim 50, whereinthe fibre layer is made of glass fibres.
 52. The battery according toclaim 50, wherein the fibre layer is made of silicate fibres or of amixture of glass fibres and silicate fibres.
 53. The battery accordingto claim 50, wherein fibres of the fibre layer have a length of morethan 30 mm.
 54. The battery according to claim 50, wherein the heatinsulation element is less than 6 mm, in particular between 2 and 3 mm,thick.
 55. The battery according to claim 50, wherein at least one ofthe cover layers is formed as a heat-resistant metal layer, preferablyaluminium foil.
 56. The battery according to claim 50, wherein at leastone of the cover layers is a heat-resistant mica layer, preferably micapaper layer or mica board.
 57. The battery according to claim 50,wherein the first cover layer is a mica layer, preferably mica paperlayer, and the second cover layer is an aluminium layer, preferablyaluminium foil.
 58. The battery according to claim 50, wherein the coverlayers are connected to each other by means of adhesive bonding.
 59. Thebattery according to claim 50, wherein the heat insulation element has adielectric strength of more than 20 kV/mm.
 60. The battery according toclaim 50, wherein the heat insulation element, on at least one flatside, is self-adhesive at least in sections or has an adhesive layer.61. The battery according to claim 50, wherein the heat insulationelement has a compression hardness of less than 40 kPa.
 62. The batteryaccording to claim 50, wherein the heat insulation element is attachedand/or fixed, preferably glued, to an inner side of a housing lid and/orhousing upper part of the housing.
 63. The battery according to claim50, wherein the heat insulation element for thermal insulation isarranged between two adjacent battery cells of the battery.
 64. Thebattery according to claim 50, wherein battery cells of the battery areat least substantially completely and/or on all sides enclosed orsurrounded by one or more heat insulation element.
 65. A lithium-ionbattery for an electric vehicle, with a housing, and with at least onemulti-layer heat insulation element arranged in the housing for thermalinsulation, the multi-layer heat insulation element being overallflexible and compressible and comprising a long-fibre, needled nonwovenas fibre layer the multi-layer heat insulation element is arrangedbetween adjacent battery cells and/or above battery cells in a housingof the battery for thermal insulation, the fibres of the fibre layerhaving a length of more than 30 mm.
 66. The battery according to claim65, wherein the battery and/or the housing has an outlet for the escapeof gases, wherein the heat insulation element covers the outlet.
 67. Thebattery according to claim 65, wherein the heat insulation element has acompression hardness of less than 40 kPa, wherein the heat insulationelement has a dielectric strength of more than 20 kV/mm, and wherein theheat insulation element has at least one mica layer.
 68. A battery, witha housing, and with at least one multi-layer heat insulation elementarranged in the housing for thermal insulation and fire protection,wherein the heat insulation element comprises a first cover layer, asecond cover layer, and a compressible and pliable intermediate plyarranged between the cover layers, the intermediate ply comprising atleast one heat-resistant fibre layer formed from a needled nonwoven, thefibres of the fibre layer having a length of more than 30 mm, the heatinsulation element having a dielectric strength of more than 20 kV/mm,wherein the two cover layers are made of mica or wherein the first coverlayer is made of mica and the second cover layer is made of metal oraluminium.